When scientists first detected gravitational waves back in February, the measurements could be likened to a "chirp" in outer space. However, scientists say that future measurements will reveal faint gravitational waves that won't be as conspicuous and will be more comparable to a hushed sound.
Using the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO), scientists could soon be able to pick up faint gravitational wave signals that stem from black hole collisions that take place too far out in space to be directly observed. They believe that detections could come as soon as a few years, which is much faster than previously believed.
When LIGO detected the original gravitational waves from the pair of merging black holes, the signal stood out fairly strongly in the data, making itself known above the bumps and wiggles in the data that frequently present themselves due to LIGO's extremely sensitive detectors.
The wave was characterized by swift rises in frequency, which were subsequently converted to sound waves that resulted in the sound of a bird's chirp, a reflection of the black holes' inward nature.
In addition to this obvious swell, LIGO data is punctuated by large numbers of smaller ripples. These faint gravitational waves occur when "you're looking at black holes which are much farther away," according to LIGO spokesperson Gabriela González.
Although LIGO is not sensitive enough to detect these waves completely, data comparison using information from LIGO's separate detectors could help scientists identify patterns that shed light on these background waves. If this is accomplished, they could eventually reveal the unique conditions that are necessary for black hole formation.
"My honest opinion was, 'I'm going to be lucky if we see this result in my lifetime,'" said Emanuele Berti, a University of Mississippi physicist who is not involved with LIGO. The new findings have made him change his tune. "Nature was good to us, and now we think that we're going to be able to see them pretty soon."
New estimates of the rate of black hole mergers suggests that there are much more happening on a regular basis than originally thought, and LIGO could be sensitive to nearly 2,000 of them a year.
"There are good prospects of all kinds - it's not just detections of single events," González said, revealing the potential of detecting faint gravitational waves to shed light on as many black hole mergers as possible.
The findings were published in the April 1 issue of Physical Review Letters.
